The present invention relates to an apparatus and method for mounting electronic components such as semiconductors on circuit boards or film carriers,.
A known method for connecting the bump electrodes of a semiconductor to the patterning electrodes of a circuit board is press-bonding the components with an insulating resin between the semiconductor and the circuit board. This method is referred to as microbump bonding. This microbump bonding method is depicted in FIG. 9.
In FIG. 9(a), circuit board 51 is composed on a material such as glass or ceramics. Patterning electrode 52 is formed on circuit board 51. A drop 53 of a light setting insulation resin is placed at a position on the circuit board where an LSI chip 13 is aligned with patterning electrode 52. Bump electrode 81 is usually formed on aluminum electrode 14 with a barrier-metal such as Ti/Pd/Au or Cr/Au placed between them.
To date, bump electrode 81 has only been comprised of a metallic material such as gold or solder. Also to date, bump electrode 81 has been formed on aluminum electrode 14 of the LSI chip 13 either directly by an electrolytic plating method, or through a transferring method whereby metal bumps formed on a separate metal substrate are transferred to the surface of aluminum electrode 14 of LSI chip 13.
As illustrated in FIG. 9(c), LSI chip 13 is applied with a pressing force exerted through a pressure application tool 42.
Insulation resin 53 under bump electrode 81 is completely displaced, and bump electrode 81 is compressed to complete an electrical connection with patterning electrode 52.
Then, ultraviolet rays 54 are irradiated for curing the light setting insulation resin 53, as shown in FIG. 9.
When the circuit board is formed of a transparent material such as glass, the ultraviolet rays are irradiated from the back side of circuit board 51. When the circuit board is not transparent, the ultraviolet ray irradiation is applied from the side where LSI chip 13 is mounted. When the resin is cured and pressure application tool 42 is removed, the connection between LSI chip 13 and circuit board 51 is completed, as shown in FIG. 9(e).
The aforementioned prior art method has the following problems:
1) As the number of connecting pins increases, their weight becomes so large as to make the semiconductor and the circuit board liable to deform. This leads to deterioration in connecting reliability and sometimes to damage of the semiconductor itself. PA1 2) The pressure application on tens to hundreds of electrodes formed on semiconductors has to be applied uniformly. Very high accuracy has to be realized in the flatness of both the pressure application tool and the opposing surface of the circuit board. The degree of accuracy required increases as the number of connecting pins increases and the chip size becomes large. This high degree of accuracy is difficult to meet. Even a small variation in the height distribution of the bump electrodes, by 3 to 5 um for example, or a slight warp of the circuit board will cause failures in connection. PA1 3) Also, when the semiconductors are turned on to operate, the heat generated from the semiconductors tends to bring about straining and warping of the materials used. This straining and warping is due to differences in the thermal expansion coefficient and also leads to failures in connection between the bump electrodes and the circuit board electrodes.
The connection failures described above take place not only with the microbump bonding method but also with the flip-chip bonding method that uses solder bumps.